Building Instructions

Connect the two motors to ports B and C
on the NXT. It doesn't matter which is which.

11

Connect the third motor to port A on the NXT,
and route the wire under the 5-hole beam as shown below.

12

Connect the touch sensor wire to port 4 on the
NXT.

13

14

Ball
Kicker Programming

Use the Kicker
program for the Ball Kicker. This program uses two different ways
to synchronize the motions of the hip and knee joints. On the
retraction, the joints are synchronized by using different power levels,
and on the strike swing the joints are synchronized by using the
rotation sensor in one of the motors.

Using the Ball Kicker

Put the Ball Kicker on
a flat surface and extend the leg so that it goes straight out to
the left when facing the NXT display, as shown in the picture below.

Press the touch
sensor. The program will retract the leg and then swing it.

Challenges

Can you make any
refinements to the mechanical design or the program to hit the ball
farther?

It would be cool if
the leg on this Ball Kicker was vertical like a real leg instead of
horizontal, because then it would look like a real leg, and gravity
would also be helping out to make the kick much stronger, but there
are not enough beams in the standard NXT set to build a frame strong
enough to support a long vertical leg. If you have a lot of
extra parts, you could give it a try. Take a look at the
Flipping_Gymnast project for an
idea of how to design a strong frame that won't knock over under
force, but the frame for a vertical Ball Kicker will need to be even
higher and more reinforced. You could also consider supporting
the leg with something like two chairs to get it up high instead of
using all LEGOs for the frame.

Some arm movements,
such as throwing a baseball or spiking a volleyball, produce an even
stronger crack-the-whip effect by synchronizing three joints:
shoulder, elbow, and then wrist. Can you design an arm that
synchronizes three joints to throw or hit something?